result.nula

// Nulang standard library — Result combinators.
// Import: `import stdlib::result`

/// The Result type: represents either success (Ok) or failure (Error).
pub type Result[T, E] = Ok(T) | Error(E)

/// Unwrap a Result, returning the Ok value.
/// Panics (via Test.assert) on Error.
pub fn unwrap[T, E](r: Result[T, E]) -> T {
    match r {
        Ok(x) => x,
        Error(_) => perform Test.assert(false, "called `unwrap` on an Error value"),
    }
}

/// Map a function over a successful Result.
pub fn map[T, U, E](r: Result[T, E], f) -> Result[U, E] {
    match r {
        Ok(x) => Ok(f(x)),
        Error(e) => Error(e),
    }
}

/// Returns true if the Result is Ok.
pub fn is_ok[T, E](r: Result[T, E]) -> Bool {
    match r {
        Ok(_) => true,
        Error(_) => false,
    }
}

/// Returns true if the Result is Error.
pub fn is_err[T, E](r: Result[T, E]) -> Bool {
    match r {
        Ok(_) => false,
        Error(_) => true,
    }
}